For a second, as the Brigadier slowed at the sight of a roadblock up ahead, he considered suggesting that he join Agent Bilberg in the helicopter, then the Brigadier had a better idea.

"Leave him with me," he said. "We'll share anything he knows. Who'd object?"

"My bosses," said Charlie Bilberg, shaking his head. "They know he wasn't in that van for a start." And then the agent's eyes flicked to the soldier approaching their car and the pump-action shotgun in his hand.

"Hey," Charlie said. "Those aren't--"

He was right. They weren't.

Exploding glass sandblasted flesh from the Brigadier's face. And by the time Agent Bilberg understood he too had been hit by flying glass, one of the Brigadier's eyes was sliding like broken yolk from beneath his fingers.

The injured Brigadier tried to say something but the windscreen had pierced his throat and the words were drowned beneath a froth of blood.

Charlie's own fingers came away red and sticky. His eyes were both there but his fingers could touch tongue where they should have found cheek. When he checked his prisoner he found the man curled beside him on the seat.

"Put down your gun."

The words were aimed at Agent Bilberg, who suddenly realized he'd picked up his own Colt and was now holding it to Prisoner Zero's head.

I don't think so.

That was what Charlie tried to say. He wasn't sure how much of it the man in the expensive suit with the swept-back hair and dark glasses actually understood. Keeping his gun firmly in place, the young CIA man reached into his jacket and retrieved a tiny cell phone, which he flicked open, speed-dialling a number. The machine stayed dead.

Charlie Bilberg glanced towards his Siemens and tried again, checking from the corner of his eye that he'd punched the right button. When nothing happened he tried it on vocal, his broken voice ordering it to dial seven.

Again nothing.

Agent Bilberg was still trying to work out what he was doing wrong when the rear door yanked open and Caid Hammou's nephew Hassan leant across Prisoner Zero and took the gun from Charlie's right hand. Two of the agent's fingers broke as the man twisted the Colt from his grasp.

The lock knife in Hassan's other hand was French, the blade a mix of high-carbon steel, chrome and molybdenum. He held it strangely, jutting from his fist, so that he could reach in, twist away the gun and cut the CIA agent's throat all in one go.

"Nasrani," Hassan said dismissively. "They get lost when their toys don't work." Picking up Charlie Bilberg's cell phone, he tossed it to a thin-faced teenager. "Dump it," he said. "Somewhere beyond Ben Guerir." The town he named was on the road to Casablanca, about an hour north of Marrakech.

"Turn it back on," he added, "just before you dump it. Oh... and lose this as well." Reaching into his pockets, Hassan produced a small box, then hesitated. "No," he said, tossing it to the brother of the suicide bomber instead. "You," he said, "lose this where it won't be found."

"Will do." The boy stripped off his stolen battledress and shrugged himself into his own jellaba, stuffing his uniform into a Nike holdall. He placed the cell-phone jammer on top and zipped the bag. "The debt is paid?"

Hassan nodded his head.

"What about that?"

"Someone else can deal with him. Hurry it up." He watched the boy walk towards a clump of palms, while he waited impatiently for the second teenager to change out of uniform.

"Come on," Hassan said. "They'll be wondering where their petite taxi's gone." He meant the Americans or the Moroccan army or Sécurité... Whichever mix was waiting two kilometres ahead for a car so anonymous it contained no tracking devices.

A minute later, both foot soldiers were gone, their absence marked by the high whine of small dirt bikes.

"Well," said Hassan. "You've really fucked up this time." He scowled at the prisoner and then at the dead CIA agent on the seat next to him. "Let's get this over with. What did you tell them?"

"The truth," said Prisoner Zero, in a voice that sounded like wind through broken pines.

"And what did they do?"

"Kicked the chair from under me and started all over again." The prisoner smiled, and as smiles went it wasn't entirely sane.

"So what did you tell them then?"

"Nothing."

"So then they demanded the truth?"

"Which I told them."

"So they kicked the chair from under you and started all over again?"

"You know how it goes," said Prisoner Zero.

"Want to tell me what brought you back to Morocco?"

Prisoner Zero thought about this and then thought some more. Finally he looked at the man who'd so recently cut Agent Bilberg's throat and shook his head. "You wouldn't believe me anyway."

"What wouldn't I believe?"

"The truth..."

"No," said Caid Hassan, nephew of Caid Hammou and de facto boss of the city's biggest crime family. "Probably not."

Retrieving Agent Bilberg's Colt, the elegantly dressed man dropped out the magazine and thumbed away all the bullets but one, then gave the gun back to Prisoner Zero and nodded at Brigadier Abbas.

"Feel free," he said.

A circle can be begun at any point. The brush is held upright in one hand with the wrist held clear of both table and paper, the circle being drawn swiftly and confidently in one clean stroke.

A circle may begin at any point. He had been told this as a child.

It can begin far away in a strange land, where sun-bleached palms fill a tired grove and smoke rises from an ancient vehicle or it can begin closer to home, just outside the walls of the Zigin Chéng, or within the Forbidden City itself. It can begin with a word or a kiss, in flames or ice or the cold darkness of a night sky with the stars looking down on things that should not be seen.

Although he was tired to the bone and restless with waiting for death the fifty-third Chuang Tzu was nothing like as old as he felt. He was, however, exhausted. And he had been fighting with himself for longer than he could remember and was still not sure who was winning. So while he wrestled with his darkness and watched butterflies flit across the walled garden from where he sat under a tree, he considered something rather miraculous.

A killer was coming, the merest slip of a youth with barely enough life lived to cast a shadow. The Chuang Tzu was not sure whether to be upset or glad.

Beneath his cloak, the Emperor wore a chao pao, a formal court robe. In his case this robe was blue and decorated around the neck, across the shoulders and above the hem with embroidered five-toed dragons, conforming to the regulations for a first- or second-rank prince.

It was a wholly unsuitable garment for a man destined to wear imperial yellow and in choosing it the Chuang Tzu had offended almost everyone who was not already offended by his recent behaviour.

He had tried and probably failed to change history. He had fought battles within himself that those outside never saw. And he had fought against the rules laid down by the Library. For any Chuang Tzu to be killed would be shocking and the shock of his death would be felt through the empire like reverberations through a hollow drum.

All the same, there would be many who felt such an end was to be expected and that, on balance, the fifty-third Chuang Tzu deserved no less. The Emperor himself was one of these.

Settling back against a willow, the Emperor took a deep breath and let fear flow with the breath from his body. To live or die, the choice remained his. A single clap of the hands would be enough to summon General Ch'ao Kai to the edge of the gardens.

Once instructed, the General would post guards around the inner pavilions and the outer, around the Forbidden City and even in the two surrounding cities where the ambassadors and servitors lived.